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    Q1: To say you measured using a meter rule a length of an object 3 times to get the following readings : 61 mm , 64 mm , 65 mm how do we find out the uncertainty?

    Q2: To say you measured a diameter of a ball and the percentage uncertainty is 1 % what will be the the percentage uncertainty of its radius? (Do we divide by 2 because i remember in another question to find the perimeter of a rectangle we multiplied the uncertainty of the length and width by 2 to find the total uncertainty)
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    Uncertainty is the most accurate you can measure to/value you measured.
    So a metre rule, you can accurately measure to half a mm. So 0.5/61 times 100. Well you'd find the average of those three values and then do 0.05/average x 100
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    (Original post by eggfriedrice)
    Uncertainty is the most accurate you can measure to/value you measured.
    So a metre rule, you can accurately measure to half a mm. So 0.5/61 times 100. Well you'd find the average of those three values and then do 0.05/average x 100
    what about Q 2?
    thanks
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    The %age uncertainty in the radius is the same.
    The absolute uncertainty is half that for the diameter.
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    (Original post by Stonebridge)
    The %age uncertainty in the radius is the same.
    The absolute uncertainty is half that for the diameter.
    i dont quite follow?
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    (Original post by >>MMM<<)
    i dont quite follow?
    If you measure the diameter as, say, 100 ± 2cm that is a % uncertainty of 2% and an absolute uncertainty of ± 2cm

    You then calculate the radius as 50cm
    The actual uncertainty is also halved giving radius = 50 ± 1cm
    This is still a % uncertainty of 2%
    1 in 50 is 2%
    2 in 100 is 2%
    The % uncertainty remains the same on division (or multiplication) by a pure number. This is because there is no uncertainty in the value (here) of 2 that you divide the diameter by.
 
 
 
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